Considering the previously discussed differences in vitiligo prevalence between horse breeds of grey and breeds of non-grey coat colour, we examined which of the eleven annotated SNPs resulted in meaningful genotype distributions in breeds (a) selected for grey coat colour, (b) where grey coat colour occurs at low to medium level, and (c) where the grey associated STX17 mutation is not segregating. The gene discussed is STX17; the disease is vitiligo.